Top-entry rod retainer

ABSTRACT

An apparatus for use in retaining a longitudinally extending member in position relative to a spinal column includes a top-entry hook assembly (20) having a hook portion (22,28) which is engageable with a spinal column. A body (26) extending upwardly from the hook portion and has an open ended recess (32) which extends through the body and is open along one side to enable a rod or longitudinal member to be moved into the recess through the open side. An end cap (24) is engageable with the body to close the upper side opening. A clamp member or set screw (60) is disposed at the center of the end cap to clamp the rod in the recess in the body. The end cap and body are interconnectable by different types of connectors including a bayonet connector, a linear cam connector, or a threaded connector. &lt;IMAGE&gt;

BACKGROUND OF THE INVENTION

The present invention relates to an implant which engages a spinalcolumn to hold a longitudinal member or rod in position relative to thespinal column.

Spinal implants have been used in treatment of patients with deformedand/or mechanically insufficient spinal columns. Longitudinal members orrods have been contoured to a desired configuration and connected with aspinal column. Among the various devices used to connect a rod with aspinal column have been hooks having through openings which receive therod. While the hook is loose on the rod, a blade or free end of the hookis moved into engagement with the spinal column. Once the hook has beenpositioned relative to the spinal column, a set screw or clamp member istightened to securely interconnect the hook and the rod.

In the past, difficulties have been encountered in positioning the hookand rod relative to the spinal column. If the hook is placed on the rodbefore being connected with the spinal column, the rod tends tointerfere with placement of the hook relative to the spinal column. Ifthe hook is connected with the spinal column before being positioned onthe rod, difficulty may be encountered in moving the rod through anopening in the hook without disturbing the placement of the hookrelative to the spinal column.

The concept of providing a top-entry opening in a hook to receive a rodwithout sliding the hook along the rod is disclosed in U.S. Pat. No.4,269,178 issued May 26, 1981 and entitled "Hook Assembly For Engaging ASpinal Column". This patent teaches that the hook is to be held in placeby the use of a sleeve and a locking nut. The locking nut engagesexternal threads on the rod and must be threaded along the rod to aposition where the hook is to be located. In addition, the sleeve mustbe positioned on the rod adjacent to the locking nut

SUMMARY OF THE INVENTION

The present invention provides an apparatus for use in retaining alongitudinally extending member in position relative to a spinal column.The apparatus includes a top-entry hook assembly which can be positionedrelative to a longitudinal member or rod without moving the hookassembly along the rod and/or moving another article, such as a locknutor sleeve, along the rod. The hook assembly includes a body having anopen ended recess which extends through the body and is open at bothends and along one side to enable the rod to be moved into the recess. Ahook extends from a side of the body opposite from the side openingthrough which the rod is inserted into the recess. The hook isengageable with a spinal column. Once the hook has engaged the spinalcolumn and the rod has been inserted into the recess, an end cap isconnected with the body to block the side opening through which the rodwas moved into the recess. A clamp member is disposed in the center ofthe end cap to clamp the rod against the bottom of the recess in thebody.

One embodiment of the end cap includes a bayonet connector which isreadily engaged under adverse conditions which may be encountered duringan implant procedure. The bayonet connector includes flanges disposed onan upper end of the body and mating flanges disposed on the end cap.When the end cap and body are to be interconnected, the end cap istelescoped over the flanges o the body and then rotated to engage theflanges on the body with the flanges on the end cap.

Another connector for interconnecting the end cap and body includeslinear flanges on the body which engage linear flanges on the end cap.The linear flanges on either the body or end cap have cam surfaces whichinteract with other flange surfaces to hold the end cap in place. Inanother embodiment of the top-entry hook assembly, the body is providedwith an external thread convolution which is engaged by an internalthread convolution on the end cap.

In another embodiment of the top-entry hook assembly the end cap isinternal to the recess. Linear flanges on the end cap engage linearflanges on the body. A lock nut and set screw hold the end cap inposition relative to the body.

In another embodiment of the top-entry hook assembly the end cap isprovided with an alternative bayonet connector. Flanges disposed on anupper end of the body mate with flanges disposed on the end cap. Theflanges on the end cap extend into a groove formed in the body justbelow the flanges on the body. When the end cap and the body are to beinterconnected, the end cap is telescoped over the flanges on the bodyand rotated to engage the flanges on the body with the flanges on theend cap.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the invention will become moreapparent upon a consideration of the following description taken inconnection with the accompanying drawings, wherein:

FIG. 1 is an exploded illustration of a top-entry hook assemblyconstructed in accordance with the present invention; 25 FIG. 2 is apictorial illustration depicting the manner in which a hook portion ofthe top-entry hook assembly of FIG. 1 is positioned relative to a spinalcolumn, an end cap of the hook assembly having been removed;

FIG. 3 is an illustration, generally similar to FIG. 2, depicting themanner in which a longitudinal member or rod is placed in a recess inthe hook portion after the hook portion has been positioned relative tothe spinal column;

FIG. 4 is an illustration, generally similar to FIG. 3, of the top entryhook assembly with the end cap in place;

FIG. 5 is a front elevational view of the hook portion of the top-entryhook assembly of FIG. 1 and illustrating the relationship between a pairof connector flanges and an open ended recess in a body portion of thehook assembly;

FIG. 6 is a side elevational view, taken generally along the line 6--6of FIG. 5, further illustrating the construction of the hook portion;

FIG. 7 is a top plan view, taken generally along the line 7--7 of FIG.5, illustrating the configuration of a side opening through which alongitudinal member or rod is inserted into a recess in the body portionof the top-entry hook assembly;

FIG. 8 is a pictorial illustration of an end cap of the top entry hookassembly of FIG. 1, the lower side of the end cap facing upwardly toexpose a pair of connector flanges;

FIG. 9 is a bottom plan view, taken generally along the line 9--9 ofFIG. 8, illustrating the relationship of a clamp member or set screw tothe flanges on the end cap;

FIG. 10 is a sectional view, taken generally along the line 10--10 ofFIG. 9, further illustrating the construction of the end cap;

FIG. 11 is a front elevational view, generally similar to FIG. 5, of ahook portion of a second embodiment of the top-entry hook assembly;

FIG. 12 is a side elevational view, taken generally along the line12--12 of FIG. 11, further illustrating the construction of a hookportion of the top-entry assembly;

FIG. 13 is a front elevational view of an end cap which is connectedwith the hook portion of FIG. 11 to close an opening in the upper sideof a recess in the top-entry hook assembly;

FIG. 14 is a side elevational view, taken generally along the line14--14 of FIG. 13, further illustrating the construction of the end cap;

FIG. 15 is a front elevational view, generally similar to FIG. 5, of anexternally threaded hook portion of a third embodiment of the top-entryhook assembly;

FIG. 16 is a side elevational view, taken generally along the line16--16 of FIG. 15 further illustrating the construction of the hookportion of the top-entry hook assembly; and

FIG. 17 is a sectional view of an internally threaded end cap used withthe hook portion of FIGS. 15 and 16;

FIG. 18 is an exploded illustration, generally similar to FIG. 1, of ahook assembly of a fourth embodiment;

FIG. 19 is a top plan view of the hook portion of FIG. 18 illustratingthe configuration of a side opening of the top-entry hook assembly;

FIG. 20 is a front elevational view, generally similar to FIG. 5, of ahook portion of a fifth embodiment of the top-entry assembly;

FIG. 21 is an exploded view of an end cap which is connected with thehook portion of FIG. 20;

FIG. 22 is a front elevational view showing the end cap of FIG. 21connected with the hook portion of FIG. 20;

FIG. 23 is a front elevational view, generally similar to FIG. 5, of ahook portion of a sixth embodiment of the top-entry hook assembly;

FIG. 24 is a side elevational view, taken generally along the line24--24 of FIG. 23, further illustrating the construction of a hookportion of the top-entry hook assembly;

FIG. 25 is a pictorial illustration, generally similar to FIG. 8, of anend cap which is connected with the hook portion of FIG. 23, the lowerside of the end cap facing upwardly to expose a pair of connectorflanges; and

FIG. 26 is a bottom plan view taken generally along the line 26--26 ofFIG. 25.

DESCRIPTION OF SPECIFIC PREFERRED EMBODIMENTS OF THE INVENTION GeneralDescription

A top-entry hook assembly 20 constructed in accordance with the presentinvention is illustrated in FIG. 1. The top-entry hook assembly 20includes a one-piece, metal, hook portion 22 and a metal end cap 24. Thehook portion 22 includes a generally rectangular body 26 and adownwardly extending hook 28.

The body 26 of the hook portion 22 has an open ended recess 32 whichextends through the body and is open at opposite ends of the body toreceive a rod or longitudinal member. The hook 28 includes a shankportion 34 and free end or blade portion 36 which are engageable with anelement of a spinal column to interconnect the spinal column and a rodextending through the open ended recess 32.

The recess 32 has a first larger radius R1 (FIG. 5) and a second smallerradius R2. The radius R2 forms a pair of axially spaced arcuate surfaces130 (FIG. 7). The pair of axially spaced arcuate surfaces 130 engageportions of the rod at axially spaced locations. Reference is herebymade to U.S. Pat. No. 5,024,213 to Asher et al. and assigned to the sameassignee as the present invention. U.S. Pat. No. 5,024,213 describes thearcuate surfaces and their function in greater detail.

In accordance with one of the features of the present invention, the endcap 24 (FIG. 1) is removable from the hook portion 22. When the end cap24 is removed from the hook portion 22, a rectangular upper side opening40 to the recess 32 is exposed. A rod or other longitudinal member canbe readily inserted through the upper side opening 40 into the recess32.

The hook portion 22 may be mounted on a spinal column 44 by interlaminarplacement of the hook 28 as shown in FIG. 2. However, the hook 28 couldalso have supralaminar, infratransverse or supratransverse placementrelative to the spinal column 44 if desired.

Once the hook portion 22 of the hook assembly 20 has been connected withthe spinal column 44 as shown in FIG. 2, a rod or longitudinal member 48may be placed in the recess 32 (FIG. 3). The cylindrical rod 48 isplaced in the recess 32 by moving the rod downwardly through the openupper side 40 of the recess. When the rod 48 has been positioned in therecess 32, the rod extends through generally U-shaped end openings 52and 54 (FIGS. 1 and 3) disposed at opposite sides of the body 26. Whenthe rod 48 is placed in the recess 32, a longitudinal central axis 58 ofthe rod extends generally parallel to the free end or blade portion 36of the hook 28. The rod 48 is shown in FIGS. 3 and 4 as straight butwould normally be curved to a desired configuration. If desired, devicesother than the hook 28 may be used to connect the body 26 with thespinal column 44.

Once the rod 48 has been placed in the open ended recess 32, the end cap24 is connected with the hook portion 22 (FIG. 4) The end cap 24 blocksthe upper side opening 40 of the recess 22 while enabling the rod 48 toextend through the end openings 52 and 54 (FIG. 3) of the recess 32.Once the end cap 24 has been connected with the hook portion 22 of thehook assembly 20, a clamp member or set screw 60 (FIGS. 1 and 4) istightened to interconnect the rod 48 and hook assembly. The recess 32has a vertical dimension as viewed in FIG. 5 such that the rod 48 can bemoved vertically in the recess prior to the set screw 60 beingtightened.

The clamp member or set screw 60 is located at the center of the end cap24. The set screw 60 has a vertical (as viewed in FIG. 1) central axis62 which intersects the horizontal (as viewed in FIG. 4) longitudinalcentral axis 58 of the rod 48. The set screw 60 presses the rod 48against the arcuate surfaces 130 to clamp the rod against movementrelative to the hook assembly 20. In addition to pressing the rod 48against the arcuate surfaces 130, the set screw 60 applies an upwardlydirected force against the end cap 24 to retain the end cap againstdisengagement from the hook portion 22.

Since the end cap 24 is disengageable from the hook portion 22 of thehook assembly 20, the rod 48 can be readily inserted into the recess 32through the upper side opening 40. This enables the rod 48 and hookassembly 20 to be positioned relative to each other without sliding thehook assembly along the rod or moving the rod axially through the hookassembly. By mounting the clamp member or set screw 60 in the end cap24, it is not necessary to provide a clamp member which is separate fromthe hook assembly 20 and which must be positioned along the rod 48.

Hook Assembly--Bayonet Connector

In the embodiment of the hook assembly 20 illustrated in FIGS. 1 through10, a bayonet connector 64 (FIG. 1) is used to interconnect the end cap24 and hook portion 22 of the hook assembly 20. The bayonet connector 64has components which are readily positioned relative to each other by asurgeon during an operation. The bayonet connector 64 is held in anengaged condition by force transmitted between the set screw 60 and therod 48 when the top-entry hook assembly 20 is positioned relative to thespinal column 44 and connected with the rod.

The bayonet connector 64 includes a pair of flanges 68 and 70 (FIGS. 1,5, 6 and 7) disposed at the upper end of the body 26. When the end cap24 is connected with the hook portion 22, the flanges 68 and 70 areenclosed by the end cap and engage flanges 74 and 76 (FIGS. 8-10) formedon the end cap 24. When the end cap 24 is connected with the hookportion 22, flat bottom surfaces 80 and 82 on the hook portion flanges68 and 70 engage flat inwardly facing surfaces on the flanges 74 and 76on the end cap 24.

Thus, when the end cap 24 is connected with the hook portion 22, theflat lower side surface 80 on the hook flange 68 (FIG. 5) abuttinglyengages a flat inner side surface 86 (FIGS. 8 and 10) on the end capflange 74. Similarly, the flat lower side surface 82 on the hook flange70 abuttingly engages a flat inner side surface (not shown) on the endcap flange 76. Abutting engagement between the flanges 68 and 70 on thehook portion 22 and the flanges 74 and 76 on the end cap 24 hold the endcap on the hook portion 22. The end cap 24 extends across the open upperside 40 (FIG. 5) of the recess 32 to close the recess.

After the rod 48 has been inserted through the open upper side 40 of therecess 32, the end cap 24 is connected with the hook portion 22. This isaccomplished by positioning the end cap 24 in axial alignment with thehook portion 22 with the flanges 74 and 76 facing downwardly toward theflanges 68 and 70 on the hook portion 22. A transverse opening 90 (FIGS.8 and 9) between the flanges 74 and 76 on the end cap 24 is aligned withthe flanges 68 and 70 (FIG. 7) on the upper end of the hook portion 22.At this time, the flanges 68 and 70 on the hook portion 22 are offset by90° from the flanges 74 and 76 on the end cap 24.

The end cap 24 is then moved downwardly so that the flanges 68 and 70 onthe hook portion 22 are received in the opening 90. Flat upper sidesurfaces 94 and 96 (FIGS. 5 and 7) on the hook portion flanges 68 and 70are disposed in abutting engagement with a flat circular inner sidesurface 98 (FIG. 9) disposed on the end cap 24. A plurality of retaineror positioning walls 102, 104, 106 and 108 (FIGS. 8-10) engage theflanges 68 and 70 on the hook portion 22 to hold the end cap 24 in axialalignment with the hook portion 22.

The end cap 24 is then rotated through 90° relative to the hook portion22. After the end cap has been rotated through 90°, a stop surface 114(FIG. 9) formed in the end cap 24 abuttingly engages one of the flanges68 and 70 on the hook portion 22. The stop surface 114 blocks furtherrotation of the end cap 24 relative to the hook portion 22.

When the end cap 24 has been rotated through 90° relative to the hookportion 22, one of the hook portion flanges 68 and 70 engage the stopsurface 114. The flat upper side surfaces 94 and 96 (FIG. 5) on the hookportion flanges 68 and 70 are disposed in abutting engagement with theflat annular end surface 98 on a base portion 122 (FIG. 10) of the endcap 24. The flat under or lower (as viewed in FIGS. 5 and 6) sidesurface 82 of the hook flange 70 will be disposed in abutting engagementwith the flat inner side surface 86 (FIGS. 8 and 10) on the end cap 24.Similarly, the flat lower side surface 80 (FIG. 5) on the hook flange 68will be disposed in abutting engagement with an inner side surface ofthe end cap flange 76 (FIGS. 8 and 9).

Abutting engagement between the hook portion flanges 68 and 70 and endcap flanges 74 and 76 block axial movement of the end cap 24 relative tothe hook portion 22. The inner side surfaces on the end cap flanges 74and 76 extend parallel to the annular end surface 98 of the base 122.For example, the inner side surface 86 (FIG. 10) on the flange 74 isparallel to the end surface 98 of the base 122. A corresponding surfaceon the end cap flange 76 (FIG. 9) is also parallel to the base surface98 on the end cap.

Similarly, the upper and lower side surfaces on the hook portion flanges68 and 70 extend parallel to each other (FIG. 5). Thus, the lowersurfaces 80 and 82 extend parallel to the upper surfaces 94 and 96 ofthe flanges 68 and 70. Therefore, the flanges 68 and 70 on the hookportion 22 and the flanges 74 and 76 (FIGS. 8 and 9) on the end cap 24cooperate with each other in such a manner as to permit rotationalmovement of the end cap relative to the hook portion.

The clamp member or set screw 60 is received in a threaded opening 124(FIG. 10) formed in the center of the base 122 of the end cap 24. Theset screw or clamp member 24 has a central axis 62 which extendsperpendicular to and intersects the central axis 58 (FIG. 4) of the rod48 when the rod 48 is disposed in the open ended recess 32 (FIG. 3) andthe end cap 20 is connected with the hook portion 22.

When the set screw 60 is tightened or turned in the threaded opening124, a leading end surface 126 (FIG. 10) on the set screw moves intoabutting engagement with the rod 48 to press the rod against the arcuatebottom portion (FIG. 5) of the open ended recess 32. The force appliedagainst the rod 48 by the set screw 60 presses the flanges 74 and 76(FIG. 9) on the end cap 24 firmly against the flanges 68 and 70 (FIG. 5)on the hook portion 22 to hold the end cap against rotation relative tothe hook portion.

If the rod 48 has a relatively small cross section the recess 32 (FIGS.18 and 19) of the hook portion 22 includes vertical slots 140 in thesides of the upper side opening 40. The set screw 60 extends into thevertical slots 140 when the end cap 24 is connected with the hookportion 22.

Hook Assembly--Linear Cam Connector

In the embodiment of the invention illustrated in FIGS. 1-10, the endcap 24 is connected with the hook portion 22 by a bayonet connector 64.In the embodiment of the invention illustrated in FIGS. 11-14, the endcap and hook portion are interconnected by linear flange surfaces. Sincethe embodiment of the invention illustrated in FIGS. 11-14 is generallysimilar to the embodiment of the invention illustrated in FIGS. 1-10,similar numerals will be utilized to designate similar components, thesuffix letter "a" being associated with the numerals of FIGS. 11-14 toavoid confusion.

The hook portion 22a of this embodiment of the top-entry hook assemblyhas a pair of rectangular flanges 68a and 70a (FIGS. 11 and 12). Theflanges 68a and 70a extend parallel to each other and have a generallyuniform cross section throughout their length. The flanges 68a and 70aare disposed at the upper end of a generally rectangular body 26a. Ahook 28a is integrally formed with and extends downwardly from the body26a and has a shank portion 34a and a free end or blade portion 36a.

An open ended recess 32a is formed in the body 26a of the hook portion22a. The open ended recess 32a has an open upper side 40a, a generallyU-shaped end opening 52a and a second end opening corresponding to theend opening 54 (FIG. 1) of the hook portion 22.

The end cap 24a (FIGS. 13 and 14) has a pair of linear flanges 74a and76a which extend downwardly from a base portion 122a of the end cap. Thebase portion 122a has a flat rectangular lower side surface 98a. Theside surface 98a of the base 122a engages rectangular upper sidesurfaces 94a and 96a (FIG. 11) on the hook portion flanges 68a and 70a.

The lower side surface 98a of the end cap base 122a is skewed downwardlyslightly. Therefore, the distance between the lower side surface 98a andrectangular upper side surfaces of the end cap flanges 74a and 76adecreases along the length of the linear flanges. When the end cap 24ais moved along a linear path onto the hook portion 22a, the upper sidesurface 98a forms a cam which presses against the upper side surfaces94a and 96a (FIG. 11) of the hook portion flanges 68a and 70a to gripthe hook portion flanges with the flanges 74a and 76a on the end cap24a. This camming feature is optional and could be eliminated.

Once the end cap 24a has been positioned on the hook portion 22a, aclamp member or set screw 60a is rotated to apply force against the roddisposed in the open ended recess 32a to press the rod against thebottom of the recess. In addition, the force applied against the rod bythe set screw 60a results in the end cap flanges 74a and 76a beingpulled upwardly against the hook portion flanges 68a and 70a to hold theend cap against movement relative to the hook portion 22a. The set screw60a is disposed at the center of the end cap 24a.

Hook Assembly--Threaded Connector

In the embodiments of the invention illustrated in FIGS. 1-10 and 11-14flanges on the end caps cooperate with flanges on the hook portions tointerconnect the end caps and hook portions. In the embodiment of theinvention illustrated in FIGS. 16-17, a threaded connection is providedbetween the end cap and hook portion. Since the embodiment of theinvention illustrated in FIGS. 15-17 is generally similar to theembodiment of the invention illustrated in FIGS. 1-10, similar numeralswill be utilized to designate similar components, the suffix letter "b"being added to the numerals of FIGS. 15-17 to avoid confusion.

The top entry hook assembly of FIGS. 15-17 includes a hook portion 22b(FIGS. 15 and 16) having a generally rectangular body 26b with a hook28b extending downwardly from the body. The hook 28b has a shank 34bwith a free end or blade portion 36b.

The body 26b of the hook portion 22b includes an open ended recess 32b(FIG. 15). The open ended recess 32b has an open upper side 40b. Inaddition, the recess has an open end 52b and an open end opposite fromthe end 52b and corresponding to the open end 54 of the recess 32 in thehook portion 22 of FIG. 1. A rod 48 can be inserted through the openupper side 40b of the recess 32b.

In accordance with a feature of this embodiment of the invention, anexternal thread convolution 132 is formed on the upper end of the body26b. The end cap 24b (FIG. 17) has an internal thread convolution 134which is engageable with the external thread convolution 132 tointerconnect the end cap and the hook portion 22b.

Although the engagement of the internal threads on the end cap 24b withthe external threads 132 on the body 26b will interconnect the end capand body, there will be a clearance between the rod 48 and the end cap.Therefore, a clamp member or set screw 60b is provided in the center ofthe end cap 24b to clamp the rod securely in position relative to thehook 22b. When the set screw 60b is rotated to move into engagement withthe rod, force is transmitted through the set screw to the end cap 24b.This force is transmitted to the threads 132 and 134 to hold themagainst relative rotation and to securely clamp the rod in place in therecess 32b.

Hook Assembly--Internal Cap Connector

r In the embodiment of the invention illustrated in FIGS. 1-10, the endcap 24 is external to the recess 32 in the hook portion 22. In theembodiment of the invention illustrated in FIGS. 20-22, the end cap isinternally connected to the hook portion. Since the embodiment of theinvention illustrated in FIGS. 20-22 is generally similar to theembodiment of the invention illustrated in FIGS. 1-10, similar numeralswill be utilized to designate similar components, the suffix letter "c"being associated with the numerals of FIGS. 20-22 to avoid confusion.

The hook portion 22c of this embodiment of the top-entry hook assemblyhas a pair of flanges 68c and 70c (FIGS. 20 and 22). The flanges 68c and70c extend parallel to each other. The flanges 68c and 70c are disposedat the upper end of a generally rectangular body 26c. A hook 28c isintegrally formed with and extends downwardly from the body 26c and hasa shank portion 34c and a free end or blade portion 36c.

An open ended recess 32c is formed in the body 26c of the hook portion22c. The open ended recess 32c has an open upper side 40c, an endopening 52c and a second end opening corresponding to the end opening 54(FIG. 1) of the hook portion 22.

The end cap 24c (FIG. 21) has a pair of linear flanges 74c and 76c whichextend outwardly from a base portion 122c of the end cap. When the endcap 24c is moved along a linear path onto the hook portion 22c, upperside surface 98c of flanges 74c and 76c engage lower side surfaces 80cand 82c of flanges 68c and 70c (FIG. 22).

Once the end cap 24c has been positioned on the hook portion 22c, aclamp member or set screw 60c is rotated to apply force against the roddisposed in the open ended recess 32c to press the rod against thebottom of the recess. In addition, the force applied against the rod bythe set screw 60c results in the end cap flanges 74c and 76c beingpulled upwardly against the hook portion flanges 68c and 70c to hold theend cap against movement relative to the hook portion 22c. The set screw60c is disposed at the center of the end cap 24c. A lock nut 144threadably engages the set screw 60c to clamp the flanges 68c and 70c ofthe body portion 26c between the lock nut and the flanges 74c and 76c ofthe end cap 24c to further hold the end cap against movement relative tothe hook portion 22c.

As shown in FIGS. 21 and 22 the lower surface of the base portion 122cis concave to fit the rod. This concave surface also enables the cap toeasily slide along the rod to easily engage into the hook.

Hook Assembly--Alternate Bayonet Connector

In the embodiment of the invention illustrated in FIGS. 1-10, the endcap 24 includes retainer walls 102, 104, 106 and 108. In the embodimentof the invention illustrated in FIGS. 23-26, the end cap does notinclude retainer walls. Since the embodiment of the inventionillustrated in FIGS. 23-26 is generally similar to the embodiment of theinvention illustrated in FIGS. 1-10, similar numerals will be utilizedto designate similar components, the suffix letter "d" being associatedwith the numerals of FIGS. 23-26 to avoid confusion.

The body 26d (FIGS. 23-24) of the hook portion 22d has an open endedrecess 32d which extends through the body and is open at opposite endsof the body to receive a rod or longitudinal member. The hook 28dincludes a shank portion 34d and free end or blade portion 36d which areengageable with an element of a spinal column to interconnect the spinalcolumn and a rod extending through the open ended recess 32d.

In accordance with one of the features of the present invention, the endcap 24d (FIGS. 25-26) is removable from the hook portion 22d. When theend cap 24d is removed from the hook portion 22d, a rectangular upperside opening 40d (FIG. 23) to the recess 32d is exposed. A rod or otherlongitudinal member can be readily inserted through the upper sideopening 40d into the recess 32d. When the rod has been positioned in therecess 32d, the rod extends through a generally U-shaped end openings52d and a second end opening corresponding to the end opening 54(FIG. 1) of the hook portion 22.

Once the rod has been placed in the open ended recess 32d, the end cap24d is connected with the hook portion 22d. The end cap 24d blocks theupper side opening 40d of the recess 32d while enabling the rod toextend through the end openings of the recess 32d. Once the end cap 24dhas been connected with the hook portion 22d, a clamp member or setscrew 60d (FIGS. 25 and 26) is tightened to interconnect the rod andhook assembly.

The clamp member or set screw 60d is located at the center of the endcap 24d. The set screw 60d presses the rod against the bottom of therecess 32d to clamp the rod against movement relative to the hookassembly 20d. In addition to pressing the rod against the bottom of therecess 32d, the set screw 60d applies an upwardly directed force againstthe end cap 24d to retain the end cap against disengagement from thehook portion 22d.

The body 26d (FIGS. 23 and 24) of the hook portion 22d includes a pairof flanges 68d and 70d disposed at the upper end of the body. When theend cap 24d is connected with the hook portion 22d, the flanges 68d and70d are enclosed by the end cap and engage flanges 74d and 76d (FIGS. 25and 26) formed on the end cap 24d. When the end cap 24d is connectedwith the hook portion 22d, the flanges 74d and 76d on the end cap 24dengage in a groove 150 (FIGS. 23 and 24) in the body 26d. The groove 150extends entirely around the body 26d.

When the end cap 24d is connected with the hook portion 22d, the flatlower side surface 80d on the hook flange 68d (FIG. 23) abuttinglyengages a flat inner side surface 86d (FIG. 25) on the end cap flange74d. Similarly, the flat lower side surface 82d (FIG. 23) on the hookflange 70d abuttingly engages a flat inner side surface (not shown) onthe end cap flange 76d. Abutting engagement between the flanges 68d and70d on the hook portion 22d and the flanges 74d and 76d on the end cap24d hold the end cap on the hook portion 22d. The end cap 24d extendsacross the open upper side 40d of the recess 32d to close the recess.

After the rod has been inserted through the open upper side 40d of therecess 32d, the end cap 24d is connected with the hook portion 22d. Thisis accomplished by positioning the end cap 24d in axial alignment withthe hook portion 22d with the flanges 74d and 76d facing downwardlytoward the flanges 68d and 70d on the hook portion 22d. A transverseopening 90d (FIG. 25) between the flanges 74d and 76d on the end cap 24dis aligned with the flanges 68d and 70d (FIG. 23) on the upper end ofthe hook portion 22d. At this time, the flanges 68d and 70d on the hookportion 22d are offset by 90° from the flanges 74d and 76d on the endcap 24d.

The end cap 24d is then moved downwardly so that the flanges 68d and 70don the hook portion 22d are received in the opening 90d. Flat upper sidesurfaces 94d and 96d (FIG. 23) on the hook portion flanges 68d and 70dare disposed in abutting engagement with a flat inner side surface 98d(FIGS. 25 and 26) disposed on the end cap 24d.

The end cap 24d is then rotated through 90° relative to the hook portion22d. When the end cap 24d has been rotated through 90° relative to thehook portion 22d, the end cap flanges 74d and 76d engage in the groove150. The flat upper side surfaces 94d and 96d (FIG. 23) on the hookportion flanges 68d and 70d are disposed in abutting engagement with theflat end surface 98d on a base portion 122d (FIG. 25) of the end cap24d. The flat under or lower (as viewed in FIG. 23) side surface 82d ofthe hook flange 70d will be disposed in abutting engagement with theflat inner side surface 86d (FIG. 25) on the end cap 24d. Similarly, theflat lower side surface 80 (FIG. 23) on the hook flange 68d will bedisposed in abutting engagement with an inner side surface of the endcap flange 76d.

When the set screw 60d is tightened, a leading end surface 126d (FIGS.25 and 26) on the set screw moves into abutting engagement with the rodto press the rod against the bottom portion of the open ended recess 32d(FIG. 23). The force applied against the rod by the set screw 60dpresses the flanges 74d and 76d (FIG. 25) on the end cap 24d firmlyagainst the flanges 68d and 70d (FIG. 23) on the hook portion 22d tohold the end cap against rotation relative to the hook portion. Whilethe hook of FIG. 23 has been described above for use with the cap ofFIG. 25, the hook of FIG. 23 could also be used with the cap of FIG. 8if the parts are properly dimensioned.

Conclusion

In view of the foregoing description, it is apparent that the presentinvention provides an apparatus for use in retaining a longitudinallyextending member 48 in position relative to a spinal column 44. Theapparatus includes a top-entry hook assembly 20 which can be positionedrelative to the longitudinal member or rod 48 without moving the hookassembly 20 along the rod and/or moving another article, such as alocknut or sleeve, along the rod. The hook assembly 20 includes a body26 having an open ended recess 32 which extends through the body and isopen at both ends 52 and 54 and along one side 40 to enable the rod 48to be moved into the recess. A hook 28 extends from a side of the body26 opposite from the side opening 40 through which the rod is insertedinto the recess 32. The hook 28 is engageable with a spinal column 44.Once the hook 28 has engaged the spinal column 44 and the rod 48inserted into the recess 32, an end cap 24 is connected with the body 26to block the side opening 40 through which the rod 48 was moved into therecess. A clamp member 60 is disposed in the center of the end cap 24 toclamp the rod 48 against the bottom of the recess 32 in the body 26.

One embodiment of the end cap includes a bayonet connector 64 which isreadily engaged under adverse conditions which may be encountered duringan implant procedure. The bayonet connector 64 includes flanges 68 and70 disposed on an upper end of the body 26 and mating flanges 74 and 76disposed on the end cap 24. When the end cap 24 and body 26 are to beinterconnected, the end cap is telescoped over the flanges 68 and 70 onthe body 26 and then rotated to engage the flanges on the body with theflanges 74 and 76 on the end cap.

Another connector (FIGS. 11-14) for interconnecting an end cap 24a andbody 26a includes linear flanges 68a and 70a on the body which engagelinear flanges 74a and 76a on the end cap. The linear flanges on eitherthe body 26a or the end cap 24a have cam surfaces 98a which interactwith flange surfaces to hold the end cap 24a in place. In anotherembodiment of the top-entry hook assembly (FIGS. 15-17), the body 26b isprovided with an external thread convolution 132 which is engaged by aninternal thread convolution 134 on the end cap 24b.

In another embodiment of the top-entry hook assembly (FIGS. 20-22) theend cap 24c is internal to the recess 32c. Linear flanges 74c and 76c onthe end cap 24c engage linear flanges 68c and 70c on the body 26c. Alock nut 144 and set screw 60c hold the end cap 24c in position relativeto the body 26c.

In another embodiment of the top-entry hook assembly (FIGS. 23-26) theend cap 24d is provided with an alternative bayonet connector. Flanges68d and 70d disposed on an upper end of the body 26d mate with flanges74d and 76d disposed on the end cap 24d. The flanges 74d and 76d on theend cap 24d extend into a groove 150 formed in the body 26d just belowthe flanges 68d and 70d on the body. When the end cap 24d and the body26d are to be interconnected, the end cap 24d is telescoped over theflanges 68d and 70d on the body and rotated to engage flanges 68d and70d on the body with the flanges 74d and 76d on the end cap.

It should be clear that in all embodiments the recess which receives therod has the configuration shown in FIG. 5 which is described in detailin U.S. Pat. No. 5,024,213.

It should be clear from the above that modifications and changes may bemade to the present invention. For example, the connector designsdescribed above could be used on a screw or post to attach a rod to thescrew or post. In effect, the connector designs can be used with partsother than the hooks shown in the drawings. It is intended to cover allsuch modifications and changes within the scope of the appended claims.

Having described specific preferred embodiments of the invention, thefollowing is claimed:
 1. An apparatus for use in retaining alongitudinally extending member in position relative to a spinal column,said apparatus comprising a body having an open ended recess whichextends through the body and is open along one side to enable thelongitudinally extending member to be moved into the recess, said recesshaving a side opening, a first end opening formed in a first side of thebody and intersecting the side opening, and a second end opening formedin a second side of the body opposite from the first side andintersecting the side opening to enable the longitudinally extendingmember to be moved into the recess through the side opening and toextend from the first and second sides of said body through the firstand second end openings, said body including first and second flangesdisposed on opposite sides of said side opening, a connector elementextending from a side of said body opposite from the side opening andconnectable with the spinal column to connect said body with the spinalcolumn, an end cap movable between a disengaged position spaced fromsaid body and an engaged position at least partially enclosing said bodyand extending across the side opening in said body, said end capincluding a base, a first linear cam surface connected with and disposedadjacent a first side of said base, and a second linear cam surfaceconnected with and disposed adjacent to a second side of said base, saidfirst flange being engageable with said first cam surface and saidsecond flange being engageable with said second cam surface uponmovement of said end cap relative to said body along a linear path, saidfirst and second cam surfaces being disposed in a plane which extends atan acute angle to a central axis of the recess and which extends throughthe first and second end openings of the recess to enable said first andsecond cam surfaces to move said end cap toward the central axis of therecess upon movement of said end cap along the linear path, and a clampmember mounted on said end cap, said clamp member being movable relativeto said end cap when said end cap is in the engaged position to clamp alongitudinally extending member disposed in the recess against said bodyand to press said first and second cam surfaces against said first andsecond flanges to hold said end cap against movement from the engagedposition to a disengaged position.
 2. An apparatus as set forth in claim1 wherein said connector element is a hook which extends from a side ofsaid body opposite from the side opening and which is engageable withthe spinal column, said hook having a shank portion connected with saidbody and a free end portion extending from said shank portion in thedirection of a plane extending through the second side of said body toenable said hook to engage an element of the spinal column when thelongitudinally extending member is disposed in the recess.
 3. Anapparatus as set forth in claim 1 wherein said clamp member is a singleset screw which is rotatable relative to said end cap to clamp thelongitudinally extending member and said body together when thelongitudinally extending member is in the recess.
 4. An apparatus foruse in retaining a longitudinally extending member in position relativeto a spinal column, said apparatus comprising a body having an openended recess which extends through the body and is open along one sideto enable the longitudinally extending member to be moved into therecess, said recess having a side opening, a first end opening formed ina first side of the body and intersecting the side opening, and a secondend opening formed in a second side of the body opposite from the firstside and intersecting the side opening to enable the longitudinallyextending member to be moved into the recess through the side openingand to extend from the first and second sides of said body through thefirst and second end openings, said body including first and secondflanges disposed on opposite sides of said side opening, a connectorelement extending from a side of said body opposite from the sideopening and connectable with the spinal column to connect said body withthe spinal column, an end cap movable between a disengaged positionspaced from said body and an engaged position at least partiallyenclosing said body and extending across the side opening in said body,said end cap including a first surface lying in a first plane, and asecond surface lying in a second plane, said second plane extending atan acute angle to said first plane and extending at an acute angle to acentral axis of the recess, said first and second surfaces beingengageable with surfaces on said body to grip said body between saidfirst and second surfaces on said end cap, and a clamp member mounted onsaid end cap, said clamp member being movable relative to said end capwhen said end cap is in the engaged position to clamp a longitudinallyextending member disposed in the recess against said body.
 5. Anapparatus for use in retaining a longitudinally extending member inposition relative to a spinal column, said apparatus comprising a bodyhaving an open ended recess which extends through the body and is openalong one side to enable the longitudinally extending member to be movedinto the recess, said recess having a side opening, a first end openingformed in a first side of the body and intersecting the side opening,and a second end opening formed in a second side of the body oppositefrom the first side and intersecting the side opening to enable thelongitudinally extending member to be moved into the recess through theside opening and to extend from the first and second sides of said bodythrough the first and second end openings, said body including first andsecond flanges disposed on opposite sides of said side opening, aconnector element extending from a side of said body opposite from theside opening and connectable with the spinal column to connect said bodywith the spinal column, an end cap movable between a disengaged positionspaced from said body and an engaged position at least partiallyenclosing said body and extending across the side opening in said body,said end cap including a first surface having first and second endportions and a second surface having first and second end portions, saidfirst end portion of said first surface being spaced from said first endportion of said second surface by a first distance, said second endportion of said first surface being spaced from said second end portionof said second surface by a second distance, the second distance beingless than the first distance, said first and second surfaces beingengageable with surfaces on said body to grip said body, and a clampmember mounted on said end cap, said clamp member being movable relativeto said end cap when said end cap is in the engaged position to clamp alongitudinally extending member disposed in the recess against saidbody.